Binding fillers for high filler content papers by using CNF/CMF

Binding properties of fillers was developed in our study by using micro fibrillated cellulose (MFC). Savings in costs, materials and energy are striven for by increasing the filler content of the studied paper grade (SC-paper). The research hypothesis is to create mechanically stable and durable aggregates that simultaneously enhance dry and wet strength properties, filler retention and dewatering compared to traditional fillers. By developing the binding MFC-PCC aggregates it is possible to increase the filler content of papers. The new developed material combinations also open up possibilities beyond paper applications. Promising results were achieved using the MFC-PCC aggregates in high filler (40%) content PGW and TMP-based SC papers in semi-pilot scale and also pilot scale in SUORA environment at VTT. All of the most critical properties, i.e. strength, retention, dewatering, formation, smoothness, optical and predicted printing properties, either improved or achieved similar levels compared to the reference PCC in the pilot scale SUORA environment trials with on-line aggregates dosing system. In particular, IGT surface strength and Scott Bond improved significantly when MFC-PCC aggregates were used. This gives the possibility to raise the filler content of SC paper from 30% to 40% or even more. No major bottlenecks occurred in the trials. The finer VTT fine MFC provided better strength potential than the courser P2-MFC grade. The finer MFC has more specific surface area and the potential to form suitable flocs and microfilms between filler agglomerates and fibres. The long paper rolls were reeled for pilot calendering and heatset web offset (HSWO) printing tests. The performance of the novel SC papers in HSWO printing was quite good, no breaks or picking occurred and acceptable runnability and printability levels were achieved.